1. Field of the Invention
The present invention relates to a telescopic rod composed of a plurality of tubular rod sections which are mounted so as to be slidable within each other. The telescopic rod further includes a, possibly multistage, piston-cylinder unit which is arranged within the telescopic rod and is connected, on the one hand, to the outermost rod section of the telescopic rod and, on the other hand, to the last inner rod section of the telescopic rod. Locking bars are provided in the areas of the inner end faces of individual sections, wherein the locking bars are displaceable in a direction transversely of the longitudinal direction of the rod sections and wherein the locking bars can be placed in operative engagement with the respectively adjacent outer rod section. When the rod sections of the telescopic rod are in the extended end position, the locking bar of each inner rod section engages in a positively locking manner in an opening of the respectively outer adjacent rod section.
2. Description of the Related Art
Telescopic rods of the above-described type are used, for example, as telescopic jibs in a vehicle crane or rail crane, as a jib of a truck loading crane or as a telescope arm of a work platform, etc. The telescopic rod has an outer rod section and a plurality of telescoping inner rod sections. The outer rod section and the inner rod sections have a box-shaped cross section with flanges and webs, or the rod sections may also be produced from a tubular section. The device for pushing out the rod sections, usually a multistage piston-cylinder unit, is connected to the outermost rod section and the innermost rod section. In known embodiments of telescopic jibs, the device for pushing out the rod sections is fastened in fastening points at the individual sections of the parts to be telescoped. As a result, the individual cylinders or cylinder stages or the bolted connection of the outer telescope parts produce the sequence of pushing out the individual sections. Nevertheless, as is known in truck loading cranes, there is the arrangement of pushing elements mounted at the periphery of the outermost section. These embodiments are very complicated. This is true with respect to equipping individual cylinders as well as the corresponding hoses, screw connections, pipes and the respective fastening points. In addition, these embodiments are located outside of the two-axle neutral spring and, therefore, are subjected to extremely high loads when imperfections occur. The lateral free space required for these embodiments leads to additional structural limitations. These complicated constructions and embodiments are necessary for pushing the individual sections in or out in a certain sequence.